Startling Eruptions

R/V Melville began the first leg of its two-and-a-half year voyage of scientific discovery by exploring one of Earth’s most extreme environments – deep-sea volcanoes. Researchers onboard observed the first full-scale eruption of an underwater volcano in the Mariana Arc.

The research team headed by Bob Embley of the NOAA Vent Program at the Pacific Marine Environmental Laboratory in Seattle, Wash., departed Apra, Guam, on April 18, 2006, for an ongoing study of the Pacific Ring of Fire, home to more than 75 percent of the world’s volcanoes.

This mission focused on the Mariana Arc, an arch-shaped chain of active submarine volcanoes extending from the island of Guam northward more than 800 nautical miles (1450 km). They offer scientists with a spectacular view of how the ocean floor moves similar to a conveyer belt. The ocean crust in the arc represents the oldest pieces of the Pacific tectonic plate as it takes the plunge back into the earth's mantle.

The seafloor is spotted with submarine volcanoes, some of which have emerged as islands, which rise more than 3,000 meters (almost 10,000 feet) from the deep-sea floor. On April 23rd, the team dove to the ocean depths in the Jason II remotely operated vehicle to explore and sample hot springs located on active seafloor volcanoes.

While exploring the NW Rota-1 volcano, the team observed the first ever ongoing eruption of the Brimestone Pit crater.

“The volcano was belching red rock extrusions of lava and sudden bursts of gas and ash particles that, at times, enveloped the vehicle,” said Embley. “The small hydrophone we deployed nearby recorded the sounds of a seafloor eruption for the first time concurrent with visual observations. However, what was perhaps the most amazing part of the experience was the fact that we could actually observe it! It is unlikely that a similar eruption on a volcano above sea level could have been observed and sampled as thoroughly as we were able to do.”

Later in the expedition, the team discovered the first pools of liquid sulfur on submarine volcanoes in the northern part of the arc. The final dive was cut short because the Jason II broke through a crust and became partly immersed in liquid sulfur!

The research team ended their adventure in Yokohama, Japan, on May 13, 2006, where R/V Melville awaits its next scientific voyage.

— Annie Reisewitz